Questions on weightlifting

Compound moves (like the bench press) which use multiple muscles working together sometimes makes it hard to mentally focus upon one muscle over another. Two people lifting the exact same weight, one person may have stronger chest but weaker triceps/shoulders, the other person the reverse. Are they doing it wrong? As long as their form is correct, nope, they are still working the muscles. You just may have a situation where the stronger muscle is automatically compensating for the weaker, whether you are aware of the difference or not.

One way to better focus upon a single muscle is to an exercise which uses only that muscle. For chest, that might be doing a fly motion, whether with DBs or cable attachments or a machine. When only one muscle is moving, it's easier to laser focus your thoughts upon it. Yes, compound movements are generally better in terms of getting the most overall benefit for your time, working lots of muscles together, able to lift heavier than with isolation movements. But isolation moves do have their place, and sometimes that place is to help establish a better brain-muscle connection.

Another idea is to make a small mental shift in what you are trying to accomplish with your lift. For example, most new lifters with bench press think the objective is simply to move the bar away from you, which the body will do by employing its strongest muscles to make it happen. But what if you think instead about "I am trying to bring my upper arms into my chest for a hug of my mama" or "bring my elbows closer together". The overall motion remains the same, but it helps the brain to think about the elbows moving, not the bar, which can better activate the chest muscle. I do something very similar with my back, where instead of pulling a weight/bar towards me I am mentally trying to move my elbow down or back, perhaps to hit the ribs of a mugger behind me. By doing this I can shift the focus from my strong biceps towards my still-growing back muscles.